Plastic containers and bottles have been used for many years to package a wide variety of products such as milk, soft drinks, pasty foods, cosmetics, detergents, and the like. Since polyolefins such as polyethylene and polypropylene are relatively inexpensive, widely available, and easy to mold, they are most commonly used in the plastic container industry. However, it has been found that when a polyolefin bottle is used to package a beverage that contains essential oils and delicate flavor components such as a citrus juice, the juice acquires an off-flavor in a relatively short period of time. It is believed that this off-flavor is caused by the essential oils and flavoring components readily diffusing into and being absorbed by the polyolefin material. In addition, although polyolefins generally exhibit excellent moisture barrier properties, they are readily permeable to gases such as oxygen which will oxidize the various flavoring components and nutrients found in citrus juice and thereby significantly alter the juice's flavor composition and nutritional value.
In other areas of the packaging container art, there have been many attempts to improve container barrier characteristics, e.g., resistance to oxygen, moisture, and chemical permeation, by laminating a plurality of resins, each of which having different barrier properties. Particular success has been accomplished in producing high barrier containers that are made by using an injection-molded perform blow-molding process. In such a process, a laminate preform is first made by injecting a plurality of molten resin layers into an injection mold. The preform is removed from the injection mold after it has cooled and solidified. Thereafter, the preform is heated to a softened state and expanded with fluid pressure in a blow mold to form the multi-layered container. Examples of such injection-molded, laminated preforms and laminated containers made therefrom are shown in U.S. Pat. Nos. 3,955,697; 4,092,391; 4,109,813; and 4,501,781.
In addition to having good barrier properties, it is also important for a container to be of an economical size, which typically is one or two liters, or one-half or one gallon. Unfortunately, these large sized containers are bulky and difficult to handle, particularly for small children and senior adults. To provide a container with a size, shape, and handling characteristics that makes it easy to grasp and pour from, it has been found that consumers generally prefer containes that have a handle, preferably an integrally formed handle, that will permit one or more fingers to be inserted through an aperture between the handle and the container's sidewall. A well-known example of such a container is the one gallon, handled, polyethylene jug widely used to contain milk, an example of which is shown in U.S. Pat. No. 4,372,455. In order to make such a container, an extrusion blow-molding process must be used wherein a tube of thermoplastic material (a "parison") is extruded, followed by closing a blow mold around the parison such that a handle is pinched in the parison. Thereafter, the pinched parison is injected with a pressurized gas and expanded within the blow mold.
One type of plastic material that exhibits excellent flavor barrier properties is polyester, particularly polyethylene terephthalate (PET) and glycol-modified polyethylene terephthalate (PETG). Unfortunately, a container made of PET cannot be provided with an integrally-formed handle because PET cannot be extrusion blow-molded, a process which is required to make containers having an integrally molded handle as discussed above. This is because an extrusion blow-molding process can only be used when the polymer has sufficient viscosity, cohesion, and tensile strength in its molten state to support its own weight. Molten PET simply does not possess these properties.
Others have also recognized the desirability of using PET in multi-layered form, an example of which is U.S. Pat. No. 4,535,901, which issued to Okudaira et al. on Aug. 20, 1985. As disclosed therein, two or more kinds of thermoplastic resins, at least one of which being a polyester resin, is injection molded to form a multi-layered preform. The preform is then heated to an orientating temperature, followed by expanding the heated preform inside a blow mold cavity to produce a multi-layered container. As those skilled in the art will appreciate and as discussed above, it is not possible to make a container having an integral handle by using this type of process because the preform would have to be heated above its melt temperature in order to provide a good pinch-off weld or seal where the blow mold stamps a handle in the side of the preform.
In light of the above, a principal object of the present invention is to provide a multi-layered container that not only resists absorption of essential oils and flavoring components found in a delicate beverage such as a citrus juice contained therein, but also has an integrally-formed handle to make the container easy to grasp and pour from.
Another object of the present invention is to provide an extrusion blow-molded container having an integrally-formed handle with an innermost layer of PET as the container's product-contacting surface, said innermost PET layer significantly inhibiting the container's ability to absorb essential oils and flavoring components found in a delicate beverage contained therein.
A further object of the present invention is to provide an economical method of making a multi-layered container having an integrally-formed handle and a layer of PET as the container's innermost, product-contacting surface.